Pricing of nanometer-sized particles limits their market potential vs. available polymer-based materials, but new developments may open avenues, according to Nanocomposites 2002 participants.
Nanocomposites simply are not yet cost effective, said Amos Golovoy, president of consulting firm AG Research LLC in Canton, Mich., and principal organizer of the technical program for the congress, held Sept. 23-25 in San Diego.
``If one tries to use nanocomposites to improve mechanical performance of certain polymeric matrixes, one will have a great difficulty competing against other available technologies,'' such as fiberglass or carbon fiber, he said.
So far, the auto industry's approach ``has been to borrow the concept of the clay-nylon 6 nanocomposite and use it in improving properties of polypropylene and [thermoplastic polyolefin]-type materials,'' said Golovoy, who has 34 years of automotive industry experience. Those efforts face ``severe competitive pressures'' because PP or TPOs ``are not as cost effective as other available technologies.''
Incorporating nanoclay particles may ``get surfaces that are easier to paint ... and maybe improve scratch and mar resistance,'' he said.
``I know that Dow, Eastman Chemical, Honeywell [and] DuPont - not to mention compounders - are working [on nanocomposites]. They don't advertise it as such. ... No one is going to tell you what they are doing or how successful they are,'' said Golovoy.
Researchers at Florida Institute of Technology in Melbourne, Fla., demonstrated an improved thermal stability in single-screw extrusion of polymethyl methacrylate enhanced with nano-scale silica.
Increasing nano-particle concentration and decreasing particle size improved stability, said Gordon Nelson, dean of the institute's college of science and liberal arts and a plastics industry veteran.
``The material with silica in PMMA is much tougher than PMMA itself,'' Nelson said. ``On re-extrusion, one sees further enhancement of physical properties.''
In plastics, key nanocomposite properties involve flammability, impact and heat distortion, Nelson said. Use of nano-sized particle fillers can improve heat performance ``with better mechanicals [and] get a thinner cross section of parts,'' he said. `` If one can do that, much of the cost issues are actually gone.''
Nelson counsels persistence. ``Nanocomposites have a great commercial potential for plastics ... but require a good understanding of the science and engineering.''
The National Institute of Standards and Technology's building and fire research laboratory is testing high-throughput methods to study flammability and mechanical measurements of nanocomposites.
``We have taken a hiatus from just materials work to focus on these high-speed measurement techniques,'' said Jeffrey Gilman, a research polymer chemist in Gaithersburg, Md., with the materials and products group of NIST's fire science division.
Another NIST group is studying high-throughput techniques for analyzing polymers for a variety of applications.
``Layered silicate nanocomposites have been the focus of a lot of development for 20-plus years and are probably in less products than people expected'' years ago, Gilman said. ``Part of that may be because of trade-secret approaches to products.''
In recent years, at least seven patents have identified ways to use nanocomposites as a flame retardant, usually in combination with layered silicates or another approach, he said.
NIST is part of the U.S. Department of Commerce's technology administration.
Executive Conference Management Inc. of Plymouth, Mich., sponsored Nanocomposites 2002.